1. Field of the Invention
The present invention relates to antialgal compositions, methods of controlling algae, and coating compositions comprising the antialgal compositions.
2. Description of the Prior Art
The presence of algae in various aqueous systems such as latices, paints, coatings, cooling water systems, decorative ponds and the like, can cause deterioration or disfigurement of these systems. For example, painted surfaces may be disfigured by the unsightly buildup of algae, thus detracting from the overall aesthetics of the painted article; cooling towers may lose efficiency due to the buildup of algae on surfaces, thus reducing the heat transfer capabilities of the tower. It is conventional to practice methods which inhibit the algal deterioration of such systems by incorporating a variety of additives or combination of additives that are characterized by having antialgal activity.
A wide variety of materials have been used to control algae in different environments, some of which are: chlorine/bromine compounds, glutaraldehyde, isothiazolones, organotin formulations, copper salts, quaternary ammonium compounds (S D Strauss and P R Puckorius in J. Power, S1, June 1984), and triazines. Each has deficiencies related to toxicity, pH and temperature sensitivity, limited effectiveness, chemical stability, and/or compatibility.
Different diphenylethers ("DPEs") have been found to have widely different antimicrobial properties. See, for example, halogenated hydroxy (acyloxy) DPEs (U.S. Pat. Nos. 3,506,720, 3,629,477, 4,268,693, 4,339,462), substituted nitro/halo DPEs (U.S. Pat. Nos. 3,772,445, 3,908,019), and nitro/trifluoromethyl DPEs (U.S. Pat. No. 4,112,002).
U.S. Pat. No. 3,787,217 and Japanese Kokai Patent Application No. 48-48624 to Nitta et al are directed towards the use of halogenated and alkyl substituted DPEs as paint antifouling agents and disclose the use of these materials to control growth of clams, barnacles, and shellfish larvae at 0.5-1.0 ppm dosage levels. These patents do not, however, teach or suggest the use or efficacy of substituted fluoroalkyl DPEs.
Great Britain Patent No. 1592011 to Ciba-Geigy discloses the use of DPEs containing amino (or substituted amino) or hydroxy (or ester derivatives of organic/inorganic acids) substituents as algicides, particularly dichloro- and trichloro-substituted DPEs. This patent does not, however, teach or suggest the use of fluoroalkyl DPEs without hydroxy or amino substituents.
On the other hand, J. Lorenz discloses that acifluorfen (2-chloro-4-trifluoromethylphenyl-3'-carboxy-4'-nitrophenylether, sodium salt) is ineffective at all levels tested on 10 different types of algae in a screening study of commercial herbicides for use as additives in antifouling paints ("Selective Acting Antifouling Additives," Seventh Annual Congress on Marine Corrosion and Fouling, Valencia, Spain, Nov. 10, 1988).
Numerous agricultural herbicides are known to be effective in controlling specific nuisance plants (weeds), crops, etc. The modes of action of such agricultural herbicides have been extensively studied and reported in the following references: Boger et al (Z. Naturforsch, 42c, 819 (1987), 36c, 633 (1981), 39c, 486 (1984), 38c, 556 (1983); Weed Science, 33, 766 (1985), 31, 338 (1983), 29, 371 (1981), 29, 169 (1981); J Agric Food Chem, 32, 868 (1984), 32, 725 (1984), 32, 523 (1984); Pesticide Biochemistry and Physiology, 20, 183 (1983), 19, 309 (1983); IUPAC Pesticide Chemistry, Vol 3, 97-102 (1983), Vol 1, 321-326 (1983); Plant Science Letters, 24, 347 (1982). These articles report studies on the primary modes of action using a model alga, Scenedesmus acutus, to provide quick and reliable measures for understanding structure-reactivity relationships among major known herbicides, including a variety of DPEs. Boger et al observed the effect of many DPEs against various physiological and biochemical processes, concluding that it was not clear which structures are necessary to affect various modes of herbicidal action: inhibition of photosynthetic electron transport, energy transfer inhibition, and peroxidative destruction of photosynthetic membranes. The parameters measured in the mode of action studies were pigment loss (bleaching effects), short-chain hydrocarbon production due to fatty acid oxidation, reduction of photosynthetic oxygen evolution, etc. Thus, Boger et al taught that phytotoxic effects are due to the influence of more than a single biochemical mode of action. Structurally different DPEs brought about similar responses among the parameters studied by Boger et al. The relative potential of given DPEs or other herbicides to alter electron transport, peroxidation, or energy transfer modes of action is not necessarily indicative of herbicidal effectiveness. In summary, although Boger et al disclose possible pathways for herbicidal modes of action, they do not teach or suggest the use of any of these DPEs to control algae in their natural environment where water solubility, alkaline pH stability characteristics, etc., are important variables. The algae used in the Boger et al studies served only as a model to illustrate different biochemical modes of action operable with a variety of known herbicides.
Based on the aforementioned performance deficiencies of conventional antialgal compounds there is a need for more effective antialgal agents that can be used at lower dosage rates, thus being more cost effective for the end user, reducing the pollution load on the affected environmental systems, and reducing the side effects to nearby non-target organisms, such as fish, useful crops, etc.